13-32
MPC561/MPC563 Reference Manual
MOTOROLA
Programming the QADC64E Registers
Table 13-18. CCW Bit Descriptions
Bits
Name
Description
0:5
—
Reserved
6
P
Pause. The pause bit allows the creation of sub-queues within queue 1 and queue 2. The
QADC64E performs the conversion specified by the CCW with the pause bit set, and then the
queue enters the pause state. Another trigger event causes execution to continue from the pause
to the next CCW.
0 Do not enter the pause state after execution of the current CCW.
1 Enter the pause state after execution of the current CCW.
7
BYP
Sample amplifier bypass. Setting BYP enables the amplifier bypass mode for a conversion, and
0 Amplifier bypass mode disabled.
1 Amplifier bypass mode enabled.
8:9
IST
Input sample time. The IST field specifies the length of the sample window. Longer sample times
permit more accurate A/D conversions of signals with higher source impedances, especially if
BYP = 1.
00 QCKL period x 2
01 QCKL period x 4
10 QCKL period x 8
11 QCKL period x 16
10:15
CHAN
Channel number. The CHAN field selects the input channel number corresponding to the analog
input signal to be sampled and converted. The analog input signal channel number assignments
and the signal definitions vary depending on whether the QADC64E is operating in multiplexed
or non-multiplexed mode. The queue scan mechanism sees no distinction between an internally
or externally multiplexed analog input.
If CHAN specifies a reserved channel number (channels 32 to 47) or an invalid channel number
(channels 4 to 31 in non-multiplexed mode), the low reference level (VRL) is converted.
Programming the channel field to channel 63 indicates the end of the queue. Channels 60 to 62
are special internal channels. When one of these channels is selected, the sample amplifier is not
used. The value of VRL, VRH, or (VRH – VRL)/2 is placed directly into the converter. Programming
the input sample time to any value other than two for one of the internal channels has no benefit
except to lengthen the overall conversion time.
shows the channel number assignments for multiplexed mode.
Table 13-19. Non-Multiplexed Channel Assignments and Signal Designations
Non-multiplexed Input Signals
Channel Number in CHAN
Port Signal
Name
Analog Signal
Name
Other Functions
Signal Type
(I/O)
Binary
Decimal
PQB0
PQB1
PQB2
PQB3
AN0
AN1
AN2
AN3
—
I
000000
000001
000010
000011
0
1
2
3
—
PQB4
PQB5
—
AN48
AN49
Invalid
Reserved
—
I
000100 to 011111
10XXXX
110000
110001
4 to 31
32 to 47
48
49